The present invention relates to a method of producing substrate material for high temperature superconductors in which the substrate is relatively inexpensive and rapidly produced.
Considerable effort has been made in the last few years to create a robust technique for depositing long lengths of biaxially textured oxide films on metallic substrates. This effort has been manifested in a number of techniques such as ionbeam assisted deposition (IBAD), and by inclined-substrate deposition (ISD) from dual magnetron sputtering and pulsed-laser sources, as well as the RABiTS technique, see U.S. Pat. No. 5,968,877 to Budai et al. and others based on work at Oak Ridge National Laboratory. These deposition techniques require costly exciter lasers and/or complex decomposition geometries. Evaporation has long been utilized in industry as a cost-effective deposition method for continuous coating applications. Evaporation is a simple low-cost deposition technique that allows for high deposition rates.
MgO has been used successfully as a buffer layer for YBCO grown on silicon, and metal substrates. The requirement of an assisting ion gun and the addition of an amorphous Si3N4 buffer layer, make the growth of biaxially textured MgO by IBAD considerably more complex than the simplicity of evaporation on an inclined substrate. Inclined substrate deposition of oxides has played a role in creating biaxial texture in buffer layers for coated conductors, along with IBAD and RABiTS. The major hurdle in bringing these wires to market is the slow deposition rates and complex deposition systems previously required to deposit biaxially textured template layers.
Preferred orientation in MgO films grown on inclined substrates was observed previously, but it wasn""t until 1997 that this growth technique was applied to coated conductors. This invention relates to the effects of processing on the in-plane texture of MgO films grown on inclined substrates and the evolution of this texture as it pertains to developing a model for texture-development.
Biaxially textured magnesium oxide thick films were deposited using electron beam evaporation for template layers in coated conductors. Highly textured films with in-plane FWHM (Full Width Half Maximum) of 10xc2x0 were deposited at growth rates of 36 xcexcm/hr on thermally oxidized silicon and nickel-based alloy substrates. These thick films grow off-axis angled towards the atomic flux. The texturing of the MgO is a selective growth process whereby the texture improves with increasing film thickness. This growth process differs from the texturing of MgO using ion-beam assisted deposition (IBAD) which is nucleation controlled and requires an amorphous substrate. It was determined that the in plane texture of the MgO thick films are not dependent on deposition rates from 2.5 to 100 xc3x85/second, making this technique amiable to cost-effective production scale-up. This has important implications on the manufacturing scale-up of YBCO coated tapes.
Accordingly, it is an object of the present invention to provide a method of depositing a biaxially textured metal oxide on a substrate that is inexpensive while at the same time providing deposition rates up to 100 xc3x85/second in order to produce metal oxide layers of about 3 microns thick in minutes as opposed to hours.
Yet another object of the present invention is to provide a method of depositing a biaxially textured metal oxide on either a crystalline or amorphous substrate.
Yet another object of the invention is to provide a method of depositing a biaxially textured metal oxide in which a plume of metal oxide atoms is produced and thereafter the divergence thereof controlled to fabricate biaxially textured oxides with an in-plane Full-Width-Half-Maximum (FWHM) of less than about 28xc2x0.
Another object of the present invention is to provide a method of depositing a biaxially textured metal oxide on a substrate defining a plane, comprising vaporizing metal oxide atoms from a source thereof to form a plume of metal oxide atoms, and preferentially passing atoms in the plume disposed at a selected angle in a predetermined range of angles to the plane of the substrate while preventing atoms outside a selected angle from reaching the substrate.
A final object of the present invention is to provide a method of depositing a biaxially textured metal oxide on a substrate defining a plane, providing a substrate supply and a substrate storage, providing a plume of metal oxide atoms from a source of metal oxide, passing substrate from the supply thereof pass the plume of metal oxide atoms, interposing a collimator between the source of metal oxide atoms and the substrate to restrict the metal oxide atoms contacting the substrate to a selected angle within a preselected range of angles, thereby to form a biaxially textured metal oxide on the substrate from atoms contacting the substrate only at a selected angle.
The invention consists of certain novel features and a combination of parts hereinafter fully described, illustrated in the accompanying drawings, and particularly pointed out in the appended claims, it being understood that various changes in the details may be made without departing from the spirit, or sacrificing any of the advantages of the present invention.